Method for evaluating signal transmission quality

ABSTRACT

A method to assess signal transmission quality and the adjust method thereof are proposed. First, different time points of a control signal at a receiving end are acquired and the number of signal transition in a predetermined time interval is counted. Next, the number of signal transition is recorded and compared to obtain a comparison result. The quality of control signal is then determined based on the comparison result. Besides, the parameter setting of the receiving end is adjusted according to the quality of the control signal received by the receiving end to get a better performance setting.

FIELD OF THE INVENTION

The present invention relates to signal transmission quality and, more particularly, to a method for evaluating signal transmission quality.

BACKGROUND OF THE INVENTION

The DVI (Digital Visual Interface) standard is a standard for a graphics card communicating with a monitor. The DVI standard adopts transmission minimized differential signaling (TMDS) for data transmission between the graphics card and the monitor. Digital signals (including control and data information) generated by a graphics card are sent from a transmitting end through a TMDS channel (including four data lines: three data signals (RGB) and a clock signal) to a receiving end. After decoding the digital signals, the decoded signals are transferred to a digital display circuit for displaying an image on the monitor.

There are various situations (e.g., different transmission line lengths, high and low frequencies, and so on) during the process of signal transmission so that it is inappropriate for the circuits at the receiving end using the same setting to receive data under different situations. Moreover, because the transmitted data are image data, the receiving end is not able to know what the input data are and whether the input data are correct. The receiving end thus can't make the optimized adjustment corresponding to the present situation.

A conventional data recovery method for improving the signal quality at the receiving end is disclosed in U.S. Pat. No. 5,905,769. This method, however, can't effectively make the optimized adjustment in accordance with the present situation.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method to evaluate signal transmission quality.

An object of the present invention is to provide a method to adjust the parameter of the circuit at the receiving end according to a result of evaluating signal transmission quality.

According to the present invention, a method for assessing the signal transmission quality comprises: receiving a digital signal at a receiving end from a transmitting end via a channel; counting a number of transitions of the digital signal in a predetermined time interval; and determining signal transmission quality according to the number of transitions of the digital signal.

Moreover, the method may further comprise a step of selecting a setting for adjusting the parameter of the circuit at the receiving end according to the signal transmission quality.

The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of assessing signal transmission quality and performing adjustment according to an embodiment of the present invention;

FIG. 2 shows a plurality of waveforms respectively corresponding to different signal transmission quality according to the present invention;

FIG. 3 is a flowchart of assessing signal transmission quality and performing adjustment according to another embodiment of the present invention; and

FIG. 4 shows the waveforms of control signals obtained before and after signal processing of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be exemplified with but not limited to a DVI interface below.

Because there are various situations in a channel such as the impedance of a transmitting end, the length of a transmission line, the transmission speed, and so on, it is difficult for a receiving end to use the same setting for receiving signals in various situations. The present invention makes use of a digital control signal sent via the channel to the receiving end to assess the quality of the digital control signal and adjust the setting of the circuit at the receiving end based on the assessment result.

FIG. 1 shows an embodiment of the present invention. As shown in FIG. 1, a method for evaluating signal transmission quality comprises the following steps:

Step S10: reading a control signal with a format at different time, in which the control signal such as a HS (horizontal synchronization) signal, a VS (vertical synchronization) signal, a DE (data enable) signal, a HDCP (high-bandwidth digital content protection interface) or a HDMI signal (high definition multimedia interface) is transmitted from a transmitting end to a receiving end via a channel, and respectively counting a plurality of number of transitions within a time interval at different time;

Step S12: obtaining a reference value such as the difference between the maximum and the minimum of the plurality of number of transitions or/and the average of the plurality of number of transitions;

Step S14: determining the signal transmission quality according to the reference value obtained by step 12;

Step S16: classifying the factors relevant to performance of the circuits at the receiving end according to these circuits' influence on the signal transmission quality; and

Step S18: selecting an optimal setting for adjusting parameters of the circuits such as the equalizer, the impendence matching circuit, the circuit for tuning sampling phase, or the phase lock loop according to the signal transmission quality and the classifying result, while linear search, binary tree search, or importance search may be used for selecting the best setting.

In this embodiment of the present invention, smaller difference or average corresponds to a better signal transmission quality.

In this embodiment of the present invention, a plurality of setting for the circuits at the receiving end are sequentially utilized such that steps S10-S14 are performed repeatedly according to each of the plurality of setting, so as to obtain a plurality of signal transmission quality. Additionally, these signal transmission quality corresponding to the plurality of setting are used in step S18 for selecting the optimal setting among the plurality of setting. Besides, the factor of step S16 having much influence on the signal transmission quality may be first considered to introduce the plurality of setting.

In another embodiment of the present invention, a plurality of control signals such as the HS signal and the DE signal are read and respectively used for executing step S10 to step S18. These control signals may be classified according to the signal transmission quality as shown in FIG. 2.

In another embodiment of the present invention, step 12 is for comparing the plurality of number of transitions with an ideal number of transitions, respectively. [Para 26]The above embodiments can be exploited regardless of the magnitude of frequency of the control signal.

In another embodiment of the present invention as shown in FIG. 3, step S20 comprises a signal processing sub-step performing before another sub-step of step S20 for counting a plurality of number of transitions. This signal processing sub-step is for debouncing or de-glitch. Please refer to FIG. 4, which shows an embodiment reading the HS and DE control signals and performing the signal processing sub-step on these signals in step S20 of FIG. 3. The plurality of number of transitions respectively corresponding to the HS and DE signals are counted before and after the signal processing sub-step. The counting result obtained before and after the signal processing sub-step are recorded and compared in step S22, so as to get comparison results such as the differences between the maximums and minimums of the plurality of number of transitions. That is, the comparison results are the function of the plurality of number of transitions corresponding to the HS and DE signals obtained before and after the signal processing sub-step. The signal transmission quality of the control signals like the HS signal and the DE signal at the receiving end is determined in step S24 based on the comparison results. In this embodiment, the closer the maximum of the plurality of number of transitions to the minimum of the plurality of number of transitions obtained after the signal processing step, the more ideal the control signal at the receiving end, and vice versa. The signal transmission quality can thus be assessed. The subsequent steps S26 and S28 are the same as those in the previous embodiment and thus will no longer be described below.

Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims. 

1. A method for evaluating signal transmission quality, comprising: receiving a digital control signal sent from a transmitting end to a receiving end through a channel; counting a number of transitions of the digital control signal in a predetermined time interval; and determining the signal transmission quality according to the number of transitions.
 2. The method of claim 1, wherein the digital control signal is at least one of a horizontal synchronization (HS) signal, a vertical synchronization (VS) signal, and a data enable (DE) signal.
 3. The method of claim 1, wherein the digital control signal is a control signal of the high-bandwidth digital content protection (HDCP) protocol.
 4. The method of claim 1, wherein the digital control signal is a control signal of the high definition multimedia interface (HDMI) protocol.
 5. The method of claim 1, further comprising: receiving the digital control signal at different time; counting a plurality of number of transitions of the digital control signal according to the predetermined time interval; and comparing the maximum and the minimum of the plurality of number of transitions.
 6. The method of claim 5, wherein the closer the maximum to the minimum, the better the signal transmission quality.
 7. The method of claim 1, further comprising: performing a signal processing on the digital control signal for reducing a noise component of the digital control signal.
 8. The method of claim 7, wherein the signal processing includes at least one of a debouncing processing or a de-glitch processing.
 9. The method of claim 7, further comprising: counting the number of transitions before executing the step of performing the signal processing; counting the number of transitions after executing the step of performing the signal processing; and comparing the numbers of transitions obtained before and after the signal processing procedure.
 10. A method for adjusting at least a parameter of the circuit at a receiving end, comprising: receiving a control signal sent from a transmitting end to the receiving end through a channel; counting a number of transitions in a predetermined time interval, said number of transitions corresponding to the transmission quality of the control signal; comparing the number of transitions with a first value and outputting a comparison result; and adjusting the parameter of the circuit at the receiving end according to the comparison result.
 11. The method of claim 10, wherein the control signal is at least one of a horizontal synchronization (HS) signal, a vertical synchronization (VS) signal, and a data enable (DE) signal.
 12. The method of claim 10, wherein the first value is an ideal number of transitions.
 13. The method of claim 10, wherein the first value is another number of transitions obtained previously.
 14. The method of claim 10, further comprising the step of: receiving the control signal at different time; counting a plurality of number of transitions of the control signal according to the predetermined time interval; and comparing a maximum and a minimum of the plurality of number of transitions.
 15. The method of claim 14, wherein the closer the maximum to the minimum, the more ideal the control signal at said receiving end.
 16. The method of claim 10, further comprising: performing a signal processing on the control signal to reduce a noise component of the control signal.
 17. The method of claim 16, wherein the signal processing includes at least one of a debouncing processing or a deglitch processing.
 18. The method of claim 10, wherein the parameter is for adjusting an equalizer, a circuit for impedance match, a circuit for tuning sampling phase, or a phase locked loop (PLL).
 19. The method of claim 10, wherein the parameter is adjusted by using linear search, binary tree search, or importance search.
 20. The method of claim 10, further comprising: classifying the factors relevant to performance of the circuit at the receiving end according to the influence of the circuit on the transmission quality. 